Previous compensation technique for OLED displays considered backplane aging and OLED efficiency lost. The aging (and/or uniformity) of the panel was extracted and stored in lookup tables as raw or processed data. Then a compensation block used the stored data to compensate for any shift in the electrical parameters of the backplane (e.g., threshold voltage shift) or the OLED (e.g., shift in the OLED operating voltage). Such techniques can be used to compensate for OLED efficiency losses as well. These techniques are based on the assumption that the OLED color coordinates are stable despite reductions in the OLED efficiency. Depending on the OLED material and the required device lifetime, this can be a valid assumption. However, for OLED materials with low stability in color coordinates, this can result in excessive display color shifts and image sticking issues.
The color coordinates (i.e., chromaticity) of an OLED shift over time. These shifts are more pronounced in white OLEDs since the different color components that are combined in an OLED structure used to create white light can shift differently (e.g., the blue portion may age faster than the red or green portion of the combined OLED stack), leading to undesirable shifts in the display white point, which in turn lead to artifacts such as image sticking. Moreover, this phenomenon is applicable to other OLEDs as well, such as OLEds that consist of only single color components in a stack (i.e., single Red OLED stack, single GREEN OLED stack, etc.). As a result, color shifts that occur in the display can cause severe image sticking issues.